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author | cinap_lenrek <cinap_lenrek@localhost> | 2011-05-03 11:25:13 +0000 |
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committer | cinap_lenrek <cinap_lenrek@localhost> | 2011-05-03 11:25:13 +0000 |
commit | 458120dd40db6b4df55a4e96b650e16798ef06a0 (patch) | |
tree | 8f82685be24fef97e715c6f5ca4c68d34d5074ee /sys/src/cmd/python/Doc/lib/libdbhash.tex | |
parent | 3a742c699f6806c1145aea5149bf15de15a0afd7 (diff) |
add hg and python
Diffstat (limited to 'sys/src/cmd/python/Doc/lib/libdbhash.tex')
-rw-r--r-- | sys/src/cmd/python/Doc/lib/libdbhash.tex | 88 |
1 files changed, 88 insertions, 0 deletions
diff --git a/sys/src/cmd/python/Doc/lib/libdbhash.tex b/sys/src/cmd/python/Doc/lib/libdbhash.tex new file mode 100644 index 000000000..cf4470721 --- /dev/null +++ b/sys/src/cmd/python/Doc/lib/libdbhash.tex @@ -0,0 +1,88 @@ +\section{\module{dbhash} --- + DBM-style interface to the BSD database library} + +\declaremodule{standard}{dbhash} +\modulesynopsis{DBM-style interface to the BSD database library.} +\sectionauthor{Fred L. Drake, Jr.}{fdrake@acm.org} + + +The \module{dbhash} module provides a function to open databases using +the BSD \code{db} library. This module mirrors the interface of the +other Python database modules that provide access to DBM-style +databases. The \refmodule{bsddb}\refbimodindex{bsddb} module is required +to use \module{dbhash}. + +This module provides an exception and a function: + + +\begin{excdesc}{error} + Exception raised on database errors other than + \exception{KeyError}. It is a synonym for \exception{bsddb.error}. +\end{excdesc} + +\begin{funcdesc}{open}{path\optional{, flag\optional{, mode}}} + Open a \code{db} database and return the database object. The + \var{path} argument is the name of the database file. + + The \var{flag} argument can be + \code{'r'} (the default), \code{'w'}, + \code{'c'} (which creates the database if it doesn't exist), or + \code{'n'} (which always creates a new empty database). + For platforms on which the BSD \code{db} library supports locking, + an \character{l} can be appended to indicate that locking should be + used. + + The optional \var{mode} parameter is used to indicate the \UNIX{} + permission bits that should be set if a new database must be + created; this will be masked by the current umask value for the + process. +\end{funcdesc} + + +\begin{seealso} + \seemodule{anydbm}{Generic interface to \code{dbm}-style databases.} + \seemodule{bsddb}{Lower-level interface to the BSD \code{db} library.} + \seemodule{whichdb}{Utility module used to determine the type of an + existing database.} +\end{seealso} + + +\subsection{Database Objects \label{dbhash-objects}} + +The database objects returned by \function{open()} provide the methods +common to all the DBM-style databases and mapping objects. The following +methods are available in addition to the standard methods. + +\begin{methoddesc}[dbhash]{first}{} + It's possible to loop over every key/value pair in the database using + this method and the \method{next()} method. The traversal is ordered by + the databases internal hash values, and won't be sorted by the key + values. This method returns the starting key. +\end{methoddesc} + +\begin{methoddesc}[dbhash]{last}{} + Return the last key/value pair in a database traversal. This may be used to + begin a reverse-order traversal; see \method{previous()}. +\end{methoddesc} + +\begin{methoddesc}[dbhash]{next}{} + Returns the key next key/value pair in a database traversal. The + following code prints every key in the database \code{db}, without + having to create a list in memory that contains them all: + +\begin{verbatim} +print db.first() +for i in xrange(1, len(db)): + print db.next() +\end{verbatim} +\end{methoddesc} + +\begin{methoddesc}[dbhash]{previous}{} + Returns the previous key/value pair in a forward-traversal of the database. + In conjunction with \method{last()}, this may be used to implement + a reverse-order traversal. +\end{methoddesc} + +\begin{methoddesc}[dbhash]{sync}{} + This method forces any unwritten data to be written to the disk. +\end{methoddesc} |